Elucidation of the role of nuclear proteins in discrete molecular processes may provide insight into important mechanisms involved in regulation of cell growth and its aberration in neoplasia. Recently, we have shown that a nuclear protein which is tightly associated with the nuclear matrix (termed "numatrin") may have an important role in the regulation of cell growth in normal and in neoplastic lymphocytes. Experiments are proposed to examine the role of numatrin in nuclear processes associated with receptor mediated induction of mitogenesis in normal in normal lymphocytes, and with induction of growth arrest in neoplastic leukemic cells. Experiments employing affinity purified numatrin and anti-numatrin antibodies will be designed to study the role of numatrin in discrete nuclear processes which are induced by growth regulating signals in normal lymphocytes and leukemic cells. These studies will examine whether phosphorylation of numatrin, its nuclear compartmentalization and translocation from the nucleoplasm to the nucleoli (and vice versa) are processes associated with signalling of growth regulation. Further studies will be done to identify molecular interactions numatrin with nuclear components which may be regulated by mitogenic signalling, including RNA complexes, the nuclear matrix and specific nuclear proteins. We will examine whether numatrin is a DNA binding protein or is a precursor of an active DNA binding peptide derived from it by proteolytic cleavage during the cell cycle. These results will provide the basis for in vitro studies in cell free systems. The effect of purified numatrin and numatrin antibody will be examined in transcription and replication assays in isolated nuclei in order to elucidate a role for numatrin is in RNA and/or in DNA synthesis. Further, a fusion microinjection technique (using erythrocyte ghost mediated cell fusion) will be established in order to examine whether microinjection with numatrin antibody blocks the progression of lymphocytes through the cell cycle or arrest the growth of leukemic cells. These studies will provide insight into the physiological significance and the mechanisms of numatrin regulation of cell growth at distinct periods of the cell cycle and will promote our understanding of specific nuclear processes which are involved in the regulation of cell growth in normal and in neoplastic cells.